Hvac roof curb retrofit

ABSTRACT

A ventilation adapter unit or roof curb retrofit is provided for reducing energy costs in operating a building ventilation system. The unit is disposed between a traditional HVAC unit and a surface of the building, and has a plurality of internal passageways including a return air passageway, a discharge air passageway, and a supplemental discharge air passageway. Air entering the discharge air passageway from the HVAC unit is selectively routed into the supplemental discharge air passageway, where it is cooled by a cooling panel according to the position of a damper in the discharge air passageway. The cooling panel receives chilled fluid from a chiller, such as an ice storage system that operates a refrigeration unit during off-peak hours. Regardless of whether the air is routed through or around the damper, the air is then discharged from the retrofit unit and into the building.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. provisional application Ser. No. 62/008,775, filed Jun. 6, 2014, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to ventilation systems for buildings, and more particularly, to adapters or retrofit units for mounting a powered HVAC unit along a building exterior.

BACKGROUND OF THE INVENTION

Heating, ventilation, and air conditioning (“HVAC”) units are typically mounted to building rooftops, or other building exterior surfaces, at a flashed-in “curb” that is made up of a plurality of upraised walls surrounding an opening in the building exterior. Such HVAC units typically include at least a refrigerant-based air conditioning system including a compressor, an evaporator, a condenser, an electric blower, and associated ductwork contained within a main housing, with the unit made weather-resistant for outdoor installations. Optionally, HVAC units may further include a heater, such as electric coils or a gas-fired burner, and may be operable in a fan-only mode for ventilation purposes.

In some cases, and especially when a newer HVAC unit is to be installed at an existing roof curb, a roof curb adapter is placed between the HVAC unit and the roof curb to obviate the need for modifying or re-sealing the roof curb, and also to obviate the need to locate or custom build an HVAC unit having inlets and outlets that dimensionally match the outlets and inlets of an existing roof curb and associated building ductwork.

Electrical rates typically fluctuate according to the time of day and even the day of the week due to changes in demand. For example, utility companies must provide enough electrical generating capacity to meet customer demand during peak consumption times of the day, such as hot summer afternoons. However, energy demands are substantially less during cooler nighttime hours, so that substantial excess capacity is available during those hours, and energy pricing can be reduced substantially during those times. To take advantage of the lower cost energy available during “off hours,” ice storage systems have been developed to create ice or other cooled substances during off hours by operating refrigeration systems associated with the ice storage systems. The formed ice or other chilled material is stored in insulated containers, so that a separate cooling fluid may be circulated through the ice or other chilled substance during peak daytime hours, and then through a heat exchanger in a discharge air duct that supplies air to a building, to thereby cool the building during times when energy cost can be substantially higher. Thus, the cooling capacity of the ice or other chilled substance may be utilized for cooling the building air during peak hours, while reducing or eliminating the need to operate costly energy-consuming air conditioning systems, and especially their refrigerant compressors, during peak hours.

SUMMARY OF THE INVENTION

The present invention provides a modified roof curb adapter or retrofit unit, which permits the substantially conventional use of a rooftop HVAC unit, and which also permits the use of a separate chiller, such as an ice storage unit, to take advantage of lower electricity costs during off-peak hours. The retrofit unit includes a conventional return air passageway that directs warm or stale air from the building into the HVAC unit, but the retrofit unit has a damper or valve disposed along a discharge air passageway so that air received into the HVAC unit can be selectively directed through a supplemental discharge air passageway in the retrofit unit, the supplemental discharge air passageway containing a heat exchanger, such as a cooling panel associated with a chiller.

This arrangement permits the HVAC unit to be operated in a fan-only mode, without energizing a refrigerant compressor of an air conditioning system in the HVAC unit, and to instead cool the air using the cooling panel associated with the chiller, before the discharge air is passed back into the building. However, when the damper or valve is open, the air exiting the HVAC unit is routed directly through the damper or valve and out through the retrofit unit and into the building, substantially bypassing the cooling panel associated with the chiller. By essentially removing the cooling panel from the air stream when the damper or valve is open, the fan efficiency of the HVAC unit is substantially unaffected by the presence of the cooling panel in the retrofit unit, because the air discharged from the HVAC unit is not being routed through the cooling panel that otherwise causes a pressure drop in the airstream and would require higher fan power to maintain a given airflow rate. Accordingly, the HVAC unit may be operated in a conventional manner as desired, and may be operated in a fan-only mode in which air is not being cooled by the HVAC unit, but instead the air is routed along the supplemental discharge air passageway in the retrofit unit, where it passes through the cooling panel associated with the chiller, so that energy consumed by the chiller during off-peak hours may be used during on-peak hours to provide cooled air to the building during on-peak hours, as desired.

According to an aspect of the present invention, a ventilation adapter or curb retrofit unit is provided for a building ventilation system, the adapter unit including a main housing, a plurality of interior walls, a heat exchanger, and a damper. The main housing defines an inner chamber and has first and second end portions, the first end portion for engaging an exterior building surface that is associated with the building ventilation system, and the second end portion for engaging or receiving a powered ventilation unit associated with the building ventilation system. The interior walls divide the inner chamber of the main housing into a plurality of air passageways including a return air passageway that is open at both the first and second end portions of the main housing, a discharge air passageway that is open at the first and second end portions of the main housing, and a supplemental discharge air passageway having an inlet portion in fluid communication with the discharge air passageway near the open second end portion of the main housing, and an outlet portion in fluid communication with the discharge air passageway near the open first end portion of the main housing. The heat exchanger is positioned in the supplemental discharge air passageway, and is operable to add or remove heat from the flow of air passing therethrough. The damper is positioned in the discharge air passageway, between the first and second end portions of the main housing, and is positionable between an open position and a closed position. When the damper is in the open position, a flow of discharge air is permitted to pass from the powered ventilation unit through the second end portion of the main housing, and substantially directly out through the first end portion of the main housing. When the damper is in the closed position, the flow of discharge air is directed into the supplemental air passageway, through the heat exchanger, and out through the first end portion of the main housing.

Optionally, the first end portion of the housing is a lower end that engages a roof curb at the top of the building, and the second end portion of the main housing is an upper end that receives the powered ventilation unit.

Optionally, the damper includes one or more pivotable louvers and a powered actuator that pivots the louvers in response to a damper activation signal. The damper may be oriented along a diagonal (i.e. neither perpendicular nor parallel to outer walls of the retrofit unit), with a first end portion located proximate the first end portion of the main housing, and a second end portion located proximate the second end portion of the main housing.

Optionally, the interior walls include a first wall that is positioned between the damper and the inlet portion of the supplemental discharge air passageway, the first interior wall defining a generally triangular opening at the inlet portion of the supplemental discharge air passageway.

Optionally, the heat exchanger is a cooling panel having fluid conduit that is in fluid communication with a chiller, such as an ice storage unit associated with the building and operable during off-peak hours to create ice or other chilled material or substance, which can later be used to cool a fluid that is directed through the cooling panel at times when air cooling is desired, particularly during on-peak hours of higher energy costs.

Optionally, a controller is used to selectively actuate the damper to its closed position, and to activate the chiller to circulate chilled fluid through the cooling panel as air passes through the supplemental discharge air passageway and the cooling panel. The controller may be operable in response to one or more of a thermostat located in a room of the building, a real time clock, and a chiller status signal. The controller may further be operable to selectively energize the blower and compressor-based air conditioner of the powered ventilation unit. The controller may further be operable to simultaneously energize the blower of the powered roof top ventilation unit, de-energize the air conditioner of the powered rooftop unit, actuate the damper to the closed position, and activate the chiller.

Thus, the ventilation adapter unit or roof curb retrofit unit of the present invention facilitates the use of lower-priced energy during off-peak periods, and lowering energy consumption during on-peak periods, but without significantly increasing the energy consumption of a blower fan associate with a conventional HVAC unit, since a cooling panel or heat exchanger associated with the retrofit unit is essentially removed from the airstream during periods when it is not in use. The retrofit thus facilitates the installation of new HVAC units along a building exterior, without substantially affecting the operating efficiency of the HVAC unit, and by facilitating reduced usage of the HVAC unit during periods of peak energy rates or prices, by cooling discharge air using a chiller that primarily consumes energy during off-peak hours while deactivating or limiting the use of a compressor-based air conditioner associated with the HVAC unit.

These and other objects, advantages, purposes and features of the present invention will become apparent upon review of the following specification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagrammatic view of an HVAC system for a building, including a roof curb retrofit unit in accordance with the present invention;

FIGS. 2-5 are a series of top perspective views of the roof curb retrofit unit of FIG. 1, taken from different viewing angles; and

FIG. 6 is a top plan view of the roof curb retrofit unit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and illustrative embodiments depicted therein, a ventilation adapter unit in the form of a roof curb retrofit unit 10 is configured for mounting atop a building 12, between a roof curb 14 and an HVAC unit 16 (FIG. 1), although non-rooftop mounting locations are equally possible. Retrofit unit 10 has a main housing 18 with a first or lower end portion 18 a that rests atop roof curb 14, and a second or upper end portion 18 b that supports HVAC unit 16. Main housing 18 defines an inner chamber or region, which is divided into a plurality of passageways by interior divider walls. The passageways defined by main housing 18 include a return air passageway 20, a discharge air passageway 22, and a supplemental discharge air passageway 24 (FIGS. 1 and 3-6). Discharge passageway 22 contains a damper or valve 26 that is operable to selectively direct discharge air received from HVAC unit 16 into supplemental discharge air passageway 24, which contains a heat exchanger in the form of a cooling panel 28, as will be described in more detail below.

Main housing 18 has exterior surfaces made up of a plurality of panels, typically of sheet metal, including a first end wall 30 a, a second end wall 30 b, a first sidewall 32 a, a second sidewall 32 b, and a generally L-shaped bottom wall 34 at lower end portion 18 a along supplemental discharge air passageway 24 (FIGS. 3-6). Optionally, a generally L-shaped top wall, corresponding to bottom wall 34, can be positioned at upper end portion 18 b of the main housing, to enclose the supplemental discharge air passageway 24. A first interior divider wall 36 is positioned between discharge air passageway 22 and an intake end portion of supplemental discharge air passageway 24, and a second interior divider wall 38 is positioned on the opposite side of discharge air passageway 22 from first wall 36, and separates return air passageway 20 from discharge air passageway 22. First and second divider walls 26, 38 are generally parallel to first and second end walls 30 a, 30 b.

A third interior divider wall 40 is generally parallel to first and second sidewalls 32 a, 32 b, with first and second interior divider walls 36, 38 terminating at third interior divider wall 40 (FIGS. 3-6). In the illustrated embodiment, first and second divider walls 36, 38 extend inwardly from first sidewall 32 a, with first interior divider wall 36 having an extension portion 36 a projecting further toward second sidewall 32 b to accommodate cooling panel 28. However, it will be appreciated that the size and placement of cooling panel 28, and of the various sidewalls in the main housing, may be changed as desired for a particular application, without departing from the spirit and scope of the present invention.

Third interior divider wall 40 defines an opening 42 between first and second interior divider walls 36, 38, and below an upper end portion 26 a of damper 26 (FIGS. 3 and 4). Damper 26 is set at a diagonal angle, so that its upper end portion 26 a is positioned along interior divider wall 40, while a lower end portion 26 b is positioned along first sidewall 32 a at L-shaped bottom wall 34. As will be described in more detail below, when damper 26 is open, such as shown in FIGS. 2-6, discharge air entering discharge air passageway 22 at upper end portion 18 a will pass substantially uninhibited through damper 26 and out through a discharge opening 44 formed in lower end portion 18 a, between first and second divider walls 36, 38. When damper 26 is closed, discharge air is routed through a generally triangular opening 46 and into supplemental discharge air passageway 24, where it passes through cooling panel 28, whereupon it is directed out through discharge opening 44 via opening 42 formed in third interior divider wall 40. Thus, when damper 26 is closed, discharge air in the discharge air passageway 22 is forced around damper 26 and through cooling panel 28, rather than directly through damper 26, although it will be appreciated that the discharge air eventually exits through the same discharge opening 44 regardless of the position of damper 26.

Referring again to FIG. 1, return air passageway 20 receives warm or stale air from building 12 via a return air duct 48 having an inlet 48 a inside the building, and having an outlet 48 b in the roof curb 14. Similarly, all discharge air entering discharge air passageway 22 exits through discharge opening 44 and into a discharge air duct 50 having an inlet portion 50 a at roof curb 14, and an air outlet portion 50 b in a room of building 12. Return air exiting return air passageway 20 at upper end portion 18 a of the main housing passes into an intake duct 52, passes through a heat exchanger such as an evaporator 54 that receives refrigerant from a compressor 56. A condenser would also be included, and a fresh air intake and/or heater are optional, but are omitted from the drawing for clarity. It will further be appreciated that, instead of a refrigerant-based cooling system, the HVAC unit could utilize an evaporative cooling system, a piezoelectric cooling system, or substantially any other type of heat exchanger, without departing from the spirit and scope of the present invention.

After passing through evaporator 54, which may or may not be actively operating to cool the air received through intake duct 52, the air enters a discharge duct 58 containing a blower fan 60, which draws the air through return air duct 48, intake duct 52, discharge duct 58, and directs the discharge air into discharge air passageway 22 of retrofit unit 10 and, subsequently, into discharge air duct 50 and into the room of the building. It is desirable that blower fan 60 is operable independently of compressor 56 so that HVAC unit 16 may be operated in a relatively low-energy state by running only blower fan 60 for ventilation and subsequent cooling by the cooling panel 28 of retrofit unit 10. This permits discharge air to be cooled only by cooling panel 28 when damper 26 is closed.

Cooling panel 28 is another heat exchanger that receives chilled fluid via a cold fluid inlet line 62 a, which originates at a chiller such as an ice storage unit 64 located in or nearby building 12. Typically, the chilled fluid passes through coils or a series of fluid passageways of cooling panel 28, absorbing heat from the airstream as the air passes through supplemental discharge passageway 24. The fluid then exits through a fluid outlet line 62 a, which leads back to ice storage unit 64 for re-cooling and recirculation back to cooling panel 28.

A controller 66 is operable to control HVAC unit 16, damper 26, and ice storage unit 64. Controller 66 is in communication with HVAC unit 16 via an HVAC control line 68, is in communication with a powered actuator associated with damper 26 via a damper control line 70, and is in communication with ice storage unit 64 via a chiller control line 72. Preferably, controller 66 is operable to independently energize and de-energize compressor 56 and blower fan 60 of HVAC unit 16, reposition damper 26 in the open or closed position as needed, and to activate ice storage unit 64 by operating a fluid pump to direct chilled fluid into cooling panel 28 via cold fluid inlet line 62 a. In addition, controller 66 may include or be in communication with a real time clock, and with a thermostat 74 positioned in a room of the building. Optionally, the controller may be in wireless communication with the various components that it controls and/or from which it receives data that is uses to determine the appropriate operating configuration.

To operate HVAC unit 16, retrofit unit 10, and ice storage unit 64 in a cost-efficient and optimized manner, controller 66 is programmed to operate ice storage unit 64 during off-peak hours when energy costs are lower, such as at night, and during that time controller 66 may rely on compressor 56 and evaporator 54 of HVAC unit 16 to provide the necessary cooling of discharge air through discharge air passageway 22, with damper 26 open. Optionally, cooling may also be supplemented by cooling panel 28 during off-peak hours, if desired and if cooling capacity remains in ice storage unit 64. During periods of high energy costs, such as during summer daytime hours, controller 66 is programmable to operate ice storage unit 64 to pump chilled fluid through cooling panel 28, and to operate blower fan 60 without operating compressor 56, with damper 26 actuated to a closed position to direct the discharged air through supplemental discharge air passageway 24 and cooling panel 28, thereby utilizing the cooling capacity of ice storage unit 64 during periods of peak energy costs. Controller 66 may receive a status signal from ice storage unit 64, the status signal being indicative of the remaining cooling capacity of ice storage unit 64, so that controller 66 can revert to normal operation of HVAC unit 16 by operating compressor 56 and opening damper 26 to bypass cooling panel 28 when the cooling capacity of ice storage unit 64 has been depleted. It is envisioned that if ice storage unit 64 retains cooling capacity after the conclusion of a high cost energy time of day, controller 66 may continue to circulate fluid from ice storage unit 64 through cooling panel 28 until its cooling capacity has been depleted. By programming controller 66 with the times of day at which energy costs are highest and lowest, controller 66 will operate retrofit unit 10, HVAC unit 16, and ice storage unit 64 in a manner that minimizes the cost of energy utilized in cooling interior rooms of building 12.

Although the ventilation adapter or retrofit unit of the present invention is primarily described herein as a rooftop unit that operates in a coordinated manner with a powered rooftop ventilation system or unit, it will be appreciated that the ventilation adapter or retrofit unit may be installed along substantially any exterior wall or surface of a building, such as for use with a wall-mounted ventilation system. The ventilation adapter or retrofit unit may also be adapted for use in a building interior. It will further be appreciated that the ventilation adapter or retrofit unit can be readily adapted to supplement a building's heating instead of (or in addition to) the building's cooling, in substantially the same manner as described above, such as by circulating warm fluid through the retrofit unit's heat exchanger panel. In such an arrangement, the warm fluid may be created by solar heating or with electricity or other energy source during times of lower energy cost, and circulated through the heat exchanger panel during times of higher energy cost.

Therefore, the present invention provides a ventilation adapter unit or roof curb retrofit that minimizes the consumption of high cost electrical energy during peak usage times of day, by offsetting some of that energy usage with increased energy usage during lower cost times of day. An ice storage system or the like is operated during low cost periods, so that chilled fluid may be circulated through a cooling panel in the retrofit unit during high energy costs times, but substantially without increasing the energy required to force discharge air through the cooling panel during times when it is not in use. The retrofit unit is operable in coordinated manner with the HVAC unit and with the ice storage system, substantially automatically, to minimize energy costs for a particular installation.

Changes and modifications in the specifically-described embodiments may be carried out without departing from the principles of the present invention, which is intended to be limited only by the scope of the appended claims as interpreted according to the principles of patent law including the doctrine of equivalents. 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A ventilation adapter unit for a building ventilation system, said adapter unit comprising: a main housing defining an inner chamber, said main housing including first and second end portions, said first end portion configured to engage an exterior building surface associated with the building ventilation system, and said second end portion configured to engage a powered ventilation unit of the building ventilation system; a plurality of interior walls dividing said inner chamber into a plurality of passageways including (i) a return air passageway open at both said first and second end portions of said main housing, (ii) a discharge air passageway open at both said first and second end portions of said main housing, and (iii) a supplemental discharge air passageway having an inlet portion in fluid communication with said discharge air passageway near said open second end portion of said main housing and an outlet portion in fluid communication with said discharge air passageway near said open first end portion of said main housing; a heat exchanger disposed in said supplemental discharge air passageway; and a damper disposed in said discharge air passageway between said first and second end portions of said main housing and positionable between an open position and a closed position; wherein when said damper is in the open position, a flow of discharge air is permitted to pass from the powered ventilation unit through said second end portion of said main housing and substantially directly out through said first end portion of said main housing, and when said damper is in the closed position, the flow of discharge air is directed into said supplemental air passageway, through said heat exchanger, and out through said first end portion of said main housing.
 2. The ventilation adapter unit of claim 1, wherein said damper is oriented along a diagonal with a first end portion located proximate said first end portion of said main housing and a second end portion located proximate said second end portion of said main housing.
 3. The ventilation adapter unit of claim 2, wherein said plurality of interior walls comprises a first interior wall positioned between said damper and said inlet portion of said supplemental discharge air passageway, and wherein said first interior wall defines a generally triangular opening at said inlet portion of said supplemental discharge air passageway.
 4. The ventilation adapter unit of claim 1, wherein said heat exchanger comprises a cooling panel in fluid communication with a chiller.
 5. The ventilation adapter unit of claim 4, further in combination with the chiller, wherein said chiller comprises an ice storage unit.
 6. The ventilation adapter unit of claim 4, further comprising a controller, wherein said controller is operable to selectively actuate said damper to the closed position and to activate the chiller to thereby circulate chilled fluid through said cooling panel.
 7. The ventilation adapter unit of claim 6, wherein said controller is operable in response to at least one chosen from (i) a thermostat located in a room of the building, (ii) a real time clock, and (iii) a chiller status signal.
 8. The ventilation adapter unit of claim 7, wherein said controller is further operable to selectively energize a blower and an air conditioner of the powered ventilation unit.
 9. The ventilation adapter unit of claim 8, wherein said controller is operable to simultaneously (i) energize the blower of the powered rooftop ventilation unit, (ii) de-energize the air conditioner of the powered rooftop ventilation unit, (iii) actuate said damper to the closed position, and (iv) activate said chiller.
 10. A roof curb retrofit unit comprising: a main housing comprising perimeter walls that cooperate to define an inner chamber, a lower portion for engaging a roof curb, and an upper portion for engaging a powered rooftop ventilation unit; a plurality of interior walls dividing said inner chamber into a plurality of passageways including (i) a return air passageway open at both said upper and lower portions of said main housing, (ii) a discharge air passageway open at both said upper and lower portions of said main housing, and (iii) a supplemental discharge air passageway having an inlet portion in fluid communication with said discharge air passageway near said open upper portion of said main housing and an outlet portion in fluid communication with said discharge air passageway near said open lower portion of said main housing; a cooling panel disposed in said supplemental discharge air passageway between said inlet and outlet portions thereof, said cooling panel configured to permit a flow of air therethrough and to remove heat from the air; and a damper disposed in said discharge air passageway between said upper and lower portions of said main housing, wherein said damper is configurable between an open position and a closed position; wherein when said damper is in the open position, a flow of discharge air is permitted to pass from the rooftop ventilation unit through said upper portion of said main housing and substantially directly out through said lower portion of said main housing, and when said damper is in the closed position, the flow of discharge air is directed into said supplemental air passageway, through said cooling panel, and out through said lower portion of said main housing.
 11. The roof curb retrofit unit of claim 10, wherein said main housing comprises a bottom panel attached to said perimeter walls, said bottom panel defining openings only at said return air passageway and at said discharge air passageway.
 12. The roof curb retrofit unit of claim 11, wherein said damper is oriented along a diagonal relative to a horizontal plane, and comprises an upper end portion proximate said upper portion of said main housing and a lower end portion proximate said lower portion of said main housing.
 13. The roof curb retrofit unit of claim 10, wherein said plurality of interior walls comprise a first interior wall positioned between said damper and said inlet portion of said supplemental discharge air passageway, and wherein said first interior wall defines a generally triangular opening at said inlet portion of said supplemental discharge air passageway.
 14. The roof curb retrofit unit of claim 10, wherein an entirety of the flow of discharge air entering said discharge air passageway passes through said damper or said cooling panel.
 15. The roof curb retrofit unit of claim 10, wherein said cooling panel is in fluid communication with a chiller.
 16. The roof curb retrofit unit of claim 15, further comprising a controller, wherein said controller is operable to selectively actuate said damper to the closed position and to activate the chiller to thereby circulate chilled fluid through said cooling panel.
 17. The roof curb retrofit unit of claim 16, wherein said controller is operable in response to at least one chosen from (i) a thermostat located in a room of a building on which said roof curb retrofit unit is mounted, (ii) a real time clock, (iii) a chiller status signal.
 18. The roof curb retrofit unit of claim 17, wherein said controller is further operable to selectively energize a blower and an air conditioner of the powered rooftop ventilation unit.
 19. The roof curb retrofit unit of claim 18, wherein said controller is operable to simultaneously (i) energize the blower of the powered rooftop ventilation unit, (ii) de-energize the air conditioner of the powered rooftop ventilation unit, (iii) actuate said damper to the closed position, and (iv) activate said chiller.
 20. A method of operating a roof curb retrofit unit, said method comprising: directing return air from a building interior to a return air passageway of the roof curb retrofit unit; directing the return air from the return air passageway to a powered rooftop ventilation unit coupled to the roof curb retrofit unit; passing the return air through a blower of the powered rooftop ventilation unit to convert the return air to discharge air; directing the discharge air from the powered rooftop ventilation unit to a discharge air passageway of the roof curb retrofit unit; closing a damper that is disposed in the discharge air passageway to thereby direct the discharge air (i) into an inlet portion of a supplemental discharge air passageway of the roof curb retrofit unit that is in fluid communication with the discharge air passageway, (ii) through a cooling panel disposed in the supplemental discharge air passageway, and (iii) out of the roof curb retrofit unit through an outlet portion of the discharge air passageway; opening the damper to thereby direct the discharge air through the damper and directly to the outlet portion of the discharge air passageway so that the discharge air substantially bypasses the supplemental discharge air passageway; and circulating a cooling fluid through the cooling panel when the damper is closed. 